Multifocal ophthalmic lens and blank therefor



. July 2, 19351 J. H. HAMMON 2,006,638 I MULTIFOCAL OPHTHALMIC LENS ANDBLANK THEREFOR Original Filed March 27, 1934 2 Sheets-Sheet ll 4 i I.; 3/;2` yg@ O 7 I /a' @f7 N Flu f f/ wm INVENTOR. Ilj 'g dames H Hammon.

BY n /6 M ATTORNEYS.;

AJuly 2, 1935.. ..1 H, HAMMON 2,006,638

MULTIFOCAL OPHTHALMIC LENS AND BLANK THEREFOR Original Filed March 27,1954 2 Sheets-Sheet 2 N VEN 'OR. E l5 James f Ham/770m Patented July 2,1935 A UNITED STATES ambas OPHTHAIMIC LENS BLANK TBEREFOR James ll.Hammon, Vincennes, Ind.

original application March 27, 1934, serial No. 717,632. Divided andthis application April 26,

1935, Serial No. 18,445

comm. (or. ss-so *A My invention relates to multifocal ophthalmicllenses and blanks therefor. It has to'do particularly with the provisionof a novel type of lens ,and lens blank which permits of the productionof trifocal and other multifocal lenses more completely adequate to thecorrection of defective vision. J s A In the making of multifocalophthalmic lense and, particularly in the making of trifoc'al lenses,Ythere are several factors of importance which should be taken intoconsideration. Chief among these factors are the prismatic effects ofthe various portions of the lenses and the shapes of such portions bothindividually and in relation to each other.

With respect to the prismatic effects of the various portions ofmultifocal ophthalmic lenses, there are several-aspects which areparticularly important. For one thing, hitherto little consideration hasbeen given to the question of the proper location of theoptical centersof reading portions and intermediate vision portions of multifocalophthalmic lenses and little has been done to insure' the attainment ofsuch proper location.

Many prior art multifocal lenses apparently overlook the fact that therelative position of the eyes in reading is markedly different fromtheirl position in distance vision and that a somewhat similardifference exists between the position of the eyes in intermediatevision in comparison with their position in distance vision or inreading. It is customary in fitting multifocal lenses to place theoptical centers of the distance portion directly in front of the pupilswhen the patient is viewing a distant object. tient looks at a closerobject the eyes converge and the distance between the pupils is lessenedso that he -no longer sees through `the same portion of the lens. Unlessprovision is made to offset the eiIect the patient will be viewing thenear objectthrough prismatic portions of the lenses. Little or noattempt'has been made to provide reading segments whose prism basesareproperly located to compensate for the prismatic effect of the main lensand, in cooperation therewith; to produce a net correction that will befully effective.

With respect to the question vof the shapes of the various portions ofmultifocal lenses, most prior art trifocal lenses have been so made thatthey automatically present difficulties to the provision of the propershapes of the reading segment portion, the intermediate vision segmentportion and the distance portion of the lenses,

relation to the optical center of the distance When the pathis beingparticularly true in fused trifocal lenses. Consequently, little successhas been had in the marketing of such trifocal lenses. Partly because ofmanufacturing difficulties and partly because of lack of perception, theart has 6 more or less turned its back upon certain shapes of readingportions and intermediate vision portions which are particularlysuitable for. the

average user of trifocal lenses.` v,

One of the objects of this invention is to provide a fused inultifocalJophthalmic lens wherein a reading segment of prismatic form and ofprescribed prismatic effect may have its base disposed according toprescription in order that proper correction `may be effected both bythe amount of prism introduced and by the proper location of the base ofthe prism constituting such reading portion. It isalso an object of thisinvention to provide for similar correction in the intermediate visionportion. In other words, one object of my invention is to provide forthe incorporation in an ophthalmic lens of a fused prism segment ofproper prismatic strength and. with the optical center .thereof at anypoint with 25 vision portion, depending upon the correction required bylthe particular eye being tted.

Another object of this invention is to provide a fused trifocalophthalmic lens with a distance vision portion, a reading segmentportion and an intermediate vision portion, all of 'which are so shapedand located with relation to each other as to insure a maximum utilityin the performance of the functions for which they are particularlydesigned.

Various other` objects of this invention will appear as this descriptionprogresses. l

In making a trifocal lens in accordance with my invention, I provide amain lens blank of suitable form and of substantially uniform thickness.I alsoform in one side thereof a substantially spherical countersink. Ithen provide a composite `button l for fusing in the sphericalcountersink. This, composite button is prepared preferably by preparinga segment from glass of van index of refraction different from they mainlens and suitable for the reading segment, lsurrounding o1' partiallysurrounding this reading segment with an intermediate segmentof glass ofan index of refraction different from both the reading segnient and themain lens blank, and then surrounding the intermediate segment with acarrier portion of glass oi! the same index of refraction as the mainlens blank. The intermediate and reading segment are both 55 ofsubstantial thickness throughout.. When this composite buttonis fused tothe main lens-blank,

the carrier portion of the composite button will its edge and anintermediate segment which also has substantial thickness all along itsedge. The lens blank thus produced may then be ground in such a mannerthat the optical center of either minor segment may be selectivelylocated a`s desired. Because of the fact that both segments havesubstantial thickness all along their edges, prismatic power maybe'produced in either segment with the base of the prism selectivelylocated. l

This application is a division of my co-pending application Serial No.717,632, filed March 27, 1934,'which is, in turn, a division of myco-pending application Serial No. 673,708, filed May 3l, 1933. Saidapplication Serial No. 673,708 is a continuation in part of myapplications, Serial No. 503,627, filed Dec. 30, 1930, Serial No.505,807, filed December 31, 1930, and Serial 110.619.365, filed June 27,1932, the latter being a continuation in part of Serial No. 503,127, ledDec. 18, 1930. l Y

Thev preferred embodiments of my invention are shown in the accompanyingdrawings wherein similar characters of reference designate correspondingparts and wherein:

Figure 1 is an enlarged perspective view of a carrier button for areading segment button, the carrier button being of such a nature thatit may serve as theI intermediate segment of the finished lens. v

Figure 2 is an enlarged perspective view of the reading segment buttonwhich is adapted to. be disposed in the opening in the button of -Figure1.

VFigure 3 is an enlarged sectional view of a composite button whichcomprises the reading segment button and the carrier button both ofvwhich arev made of glass of a different index of refraction from themain lens blank to which the composite button is subsequently fused andeach of which is a different index of refraction from the other. I

Figure 4 is an enlarged perspective view of a carrier, button which isperforated'for the reception of a composite button made from that ofFigure 3, the carrier button being of the same index oi' Arefraction asthe main lens blank to which itis-subsequently fused. 'f

Figure 5 is an enlarged plan view of the composite button which has beenformed from the button of Figure 3 and which is tobe introduced into theperforation in the carrier button shown in Figure 4.

Figure 6 is an enlarged vertical sectional view ofthe composite buttonembodying the carrier button of Figure 4 and the composite button4 ofFigure 5, with one surface thereof made convex v'to approximate aspherical countersink to be provided in the main lens blank for-thereception thereof.

Figure 7 is a sectional view of la main lens blank, taken throughthespherical counter-sink which is provided therein.

Figure 8 is a sectional view illustrating the composite blank of Figure6 mounted in the spherical countersink in the blank of Figure 7.

Figure 9 is a sectional view of asemi-finished blank formed from thestructure shown in Figure 8.

Figure 10 is a plan view of atrifocal lens of a type which may beproduced according to my invention and wherein the intermediate visionportion embraces the reading segment and exl tends for substantialdistances on both sides thereof while the upper edges of both portionsform part of a continuousline.

Figure l1 is a vertical transverse section taken through the lens ofFigure 10 and illustrating that both the reading segment and theintermediate vision segment have substantial depth at allpointsthroughout their areas.

Figure 12 is a plan view of a modified form of composite button which Imay use in making a trifocal lens according to my invention.

Figure 13 is a plan view of a trifocal lens having an intermediatevision portion and a reading portion made bythe use of the compositebutton illustrated in Figure 12.

Figure' 14 is a sectional view taken through a portion of the lens ofFigure 13.so as to show a cross section of the intermediate visionsegment and the reading segment.

Figure is a planview oi' a modified form of trifocal lens which may bemade according to my invention and which has different shaped readingand intermediate segments.

With reference to the drawings, and particularly to Figures 1 to 11inclusive; I have illustrated how a trifocal lens may be made inaccordance with the principles of my invention. The finished lens isillustrated in Figures 10 and 11.

It will be noted from Figure 10 that in the finished lens, theintermediate vision segment is so shaped with relation to the readingsegment that the intermediate vision portion provides a substantialareafor intermediate vision on both sides of the reading portion andextending upwardly substantially to the top line of such readingportion. It will further be noted that the tops of both the readingportion and the intermediate vision portion take the form of low flatarches which are joined to the sides of such portions by small arcs.This is rendered possi- -ble by a blank structure which is now to bedescribed and which also makes possible complete control of the opticalcenter of the intermediate vision portion in addition to the control ofthe location of the optical center of thereading segment portion.

In making theV lens blank in accordance with my invention, I utilize asegment of glass I (Figure 1) suitablefor forming `the intermediatesegment of the nished lens. This segmenti is provided with an aperture 2for receiving a reading segment button 3 (Figure 2). The-aperture ,2extends entirely through the segment I and under preferred conditionsmay be producedby \punch1l18 while the glass is hot and of a viscositywhich will render this feasible. This method is more economical vthancutting or grinding the aperture, though cutting or grinding may, beresorted to if desired.. Also, I may form a hole or socket in thesegment I which does not extend entirely through this segment and whichis of a form to receive the reading segment button. This may also beaccomplished by the punching of the glass segment I while hot and, ofcourse, the punch and the hole formed thereby may be of any desiredcontour. is segment I is of a different index of refraction from thereading segment button 3 tobe disposedin the aperture 75 lliv formedtherein and is also of a diierent index of refraction from the majorblank portion to be subsequently described.

The reading segment 3 is shown in Figure 2 as resembling in area thelower halfof a circle with a low nat-arched top 4 joined to\the lowersides of the segment by short arcs Sand 6. This reading segment button 3is disposed within the aperture 2 of the segment I and is preferablyfused therein. After it has been so positioned in the member I, acomposite button is formed from these members by cutting or grinding andone shape of this composite button is illustrated in Figurev 5 of thedrawings wherein'the reading segment portion is designated 3 and theintermediate vision segment portion is designated Ia.

This composite button is thereupon tted and fused into an aperture 'Iwhich is formed in a blank 8 in the sam'e manner in which the apenture 2in segment l is formed. This blank is of a different index of refractionfrom the intermediate and reading segment portions but is of an index ofrefraction identical with the index of refraction of the major lensblank to be described.

The blank thus formed is illustrated in Figure 6 in the'conditionassumed after its lower surface has been ground to a convexcurvature 9 so that it will fit into a spherical countersink l@ of amajor lens blank ll (Figure 7). It is also shown ground with itsopposite side concave which is advisable in certain cases of fusing.This major lens blank li isformed'of glass of a diierent index ofrefraction from the intermediate and reading segment portions but of thesame index of refraction as the carrier portion il. This blank ispreferably of substantial and uniform thickness throughout. Thecountersink l@ is of larger diameter and, consequentiy, of greater depththan has been provided customarily in the prior art. Furthermore, it isofV aselected and known curvature and is preferably positioned in aselected relation to the geometrical center of the lens blank.

'Ihe composite blank is positioned in the countersink as illustrated inFigure 8 and is fused therein to form the semi-iinished lens blankillustrated in this figure. During the fusion of the composite cblank tothe major lens blank, the lowersurface of the entire composite blanktakes the curve of the countersink i@ and the carrier portion 8 mergeswith the major lens blank il so that the line of demarcationtherebetween disappears. The upper-surface of the -semi-finished blankmay then be ground to con.

vex form, for example, to the curvature indicated by the dotted lineb-b. Its under surface may then be ground to concave form, for example,to the curvature indicated by line c-c. The depth of the sphericalcountersink Ill is such and the selected curvature b-b may besuch thatboth the reading segment button and the intermediate vision segmentbutton retain their areas unchanged and have substantial thickness allalong their edges although the grinding may be continued toproducefeather edges if desired.

A semi-finished lens blank is illustrated in vFigure 9. This lons blankmay further be ground on the one side as along the line c--c.` It willbe undertood that the lens blank mal be supplied in this semi-finishedcondition by the manufacturer and that subsequently it may be ground tothe proper curvature which is so selected, relative to the curvature onthe other side of the lens blank, as to give the proper correction.

The iinished trifocal lens is vmade by cutting from the finished lensblank of Figure 9. This iinished lens embodies a distance portion I2(Figure l0), a reading portion I3 and an intermediate portion I4. Theintermediate portion Il embraces the reading portion and lies below andon both sides of the reading portion. The upper boundary line of thereading portion is substantially coincident with the upper boundary lineof the intermediate portion. As shown in Figure l1, both theintermediate and the reading segments have substantial thickness allalong their edges. Thus, there is a dividing wall between all thevarious portions of the lens of substantial depth and which issubstantially perpendicular to the surface of the lens. Howeverfasstated above, the 'grinding operations may be continued suillciently toproduce feather edges if desired along certain portions of thedivisional walls.

It will be' seen from the above that I have provided a compositestructure whose disassembled parts are of such a nature and so relatedto each other that l am able to produce a multifocal lens wherein theminor lens por, tions are prismatic and wherein the base of at least oneo these prisms may be located in any direction with relation to thecenter of the finished major lens portion. More specifically, bylocating the minor lens segments within a. carrier button which lts in aspherical countersink in the major lens blank, l may s" position theminor lens segments in sucl'i Vspherical countersink that the opticalcenter of at least one of such minor segments will be at any selectedpoint either within or outside of such segment.

1n theblank construction illustrated in. Figures l to 8 inclusive, manyadvantages accrue from the fact that the combined intermediate andreading segments are carried by a carrier portion ofthe same index ofrefraction as the main lens blank. One of these advantages arises fromthe fact that the outer periphery of this intermediate vision segment isindependent of the outer periphery of the spherical countersink. Inother words, the carrier` portion provides glass of the same index ofrefractionas thelnaior lens blank to ll in around the sides of thecomposite button within the countersink. This provides submerged sidewalls for the intermediate and reading portions which permits theseportions to be further ground prismatically after fusion. Also thecarrier button may be provided with an aperture of anyr shape to receivethe composite reading and intermediate vision segment buttons.

In Figures 12, 13 and 14, l. have illustrated a modified form oftrifocal lens which may be made in accordance with my invention and'.fused to the lens blank will become anA indistinguishable part thereof.Consequently, as in the other structure, the blank produced will have anintermediate and reading segment embedded therein or a substantial depththroughout their entire areas, though further grinding may be resortedto to produce feather edges. i

In this lens, the distance field l5 occupies the major portion thereof,being locatedabove the intermediate and reading segments and alsoextending around the sides and bottom thereof.s Thus, an object at adistance may be readily observed through the upper portion of the lensand through the sides thereof while objects 'on the floor or ground maybe readily observed through the lower portion of the distance field.

The intermediate vision portion I6 and the reading portion Il arepreferably so formed that the optical center is located as at I8. Inthis position, it is nea'r the dividing line between these two segments,so that the eye in passing across this dividing line is not annoyed byany apparent jumping of the image. On the other hand, this opticalcenter is, due to the relatively fiat upper edge of the intermediateportion, also located not far from the upper dividing line between theintermediate vision portion and the distance portion of the lens. Thisalso precludes any material jump of the image as the eye passes acrossthis upper dividing line.

Another advantageous feature of this type of trifocal lens arises fromthe fact that the intermediate field of vision permits abroad lateralrange of vision so that the wearer may readilyl observe a .comparativelybroad expanse of desk, workbench or other surface. At the same time, thereading segment has an upper edge which is amply wide tovpermit adequatevision immediately below such upper edge laterally in all movements ofthe eye normally used in reading.

The structure of the blank from which this ,l lens is made permits ofthe incorporation of additional prism powers in the reading andintermediate vision segments. Likewise, the bases of these -prisms maybe located in any prescribed relation to the geometrical center of thelens. As shown in Figure 14, when this lens is finished .from the lensblank, it is ground in such a manner that the shoulder or thick edge atthe extreme lower end of the reading segment I1 is substantiallyeliminated and a feather' edge is formed and, consequently, the base ofthe prism in the reading segment will be disposed adjacent the top edgethereof. However, the lens blank may be ground differently tolocate thebase of L this figure the finished lens is shown as comprisinga'distance portion-I9, an intermediate portion 20 and a reading portion2|. The intermediate and reading portions are located in the lowerportion of the distance portion and the intermediate portion entirelysurrounds the reading portion. Both the reading portion and theintermediate portion have a substantially semiv circular lower edgejoined to a substantially flat upper edge by two short arcs, as shown.

Because it is possible to provide a carrier button or portion with anaperture `therein of lany selected shape for the reception of the com#posite reading and intermediate vision segment button, these segmentbuttons may be made of shapes not hitherto attainable economically infused trifocal lenses. For example, an intermediate vision segment ofthe shape shown in Figure 13 has not hitherto been attainable in thetypes of unfinished lens blanks found in the prior art. This has beendue particularly to the necessity for having the glass surrounding thereading segment button of circular form at the outer periphery of thespherical countersink. This factor has also placed a limitation upon thevariation in shape of the reading segment button. But with my describedblank structure, practically any shape of reading segment andintermediate vision segment is attainable in a trifocal lens blank andlens in a practicable and economical way.

Another advantageous feature of my invention.

arises from lthe fact that the lower portion .of

'oneV of the segment buttons approximates a half circle. One result ofthis is that the operator, in performing the grinding operation, needonly observe the bounding wall from time to time to be sure that itsdepth is being progressively diminished to an equal extent all around insuch cases ment is locatedl an equal distance from all points of ltheboundary wall.

A still further advantage of my lens construction is that it embodies areading segment, and in some cases an intermediate vision segment,having a wide visual area of substantial height along the upper edgethereof whose lateral bounding walls take the form of arcs whichapproximate the radius of the pupil and which join the semi-circularparts of the segments to the comparatively low arches or substantiallyflat lines that form the tops thereof. These low arches andthe arcswhich connect them to the semi-circular portion of the segments reduceundesirable refiections to a minimum. Likewise,

sharp upper corners of the segments, rendered practically necessary byprevious blank construction, which are inefficient as portions of eldsof vision. and which subtract from the areas of the distance fields areentirely dispensed with by the use of my blank construction and by theshape of segments indicated.

Anotherl advantage of my invention consists in the fact that it makespossible the construction of a trifocal lens wherein an intermediatefield of vision surrounds or substantially surrounds the reading segmentand is Dconcentric or eccentric with relation thereto. Furthermore, itis possible to construct a trifocal lens with the reading segment of anydesired shape and with the intermediate segment of any desired shape.Throughout this specification, I have used the terms reading portion,intermediate vision portion anddistance vision portion to indicateportions of different focal powers especially fitting them for theirspecific uses. It will be understood, however, that these variousportions are not limited to those positions in the lens in which vI haveshown them. They are interchangeable as to location without departingfrom the spirit of my invention. Thus, the reading,

where the optical center of the said seg- Changes such as these areWithin the scope'of my invention.

Various other advantages of my invention will appear from the appendedclaims.

Having thus described my. invention, what I claim is:

1. An unfinished fused lens blank for multifocal lenses having more thantwo fields of vision which comprises a major blank portion of an indexcf refraction suitable for distance vision, and a composite piece ofglass embodying a segment of a second index of refraction suitable forreading and a segment of a third index of refraction suitable forintermediate Vision, said composite piece of glass having an opticallyprepared surface of continuous curvature embedded insaid major blankportion to a substantial depth throughout its entire area.

2. A trifocal lens in which the major portion is formed of glass havingan index of refraction suitable for distance vision, a segment for nearvisionfused in said lens and a segment for intermediate vision of stilldifferent index fused in said lens, having a common embedded lsurface,both of said segments having thick edges and being embedded asubstantial depth in the major portion throughout their areas.

3. An unfinished lens blank for multifocal 'lenses having more than twofields of vision 5. A finished lens blank comprising a major blankportion of one index of refraction, a reading segment portion of asecond indexof refraction and an intermediate vision segment portion ofa third index of refraction, said last two portions having their edgesfused together and being fused and embedded in said major blank portionto a substantial depth throughout their entire areas with innerlenticular surfaces of merging curvature.

6. A trifocal lens consisting of a major portion of glass of one indexof refraction, an intermediate portion of glass of another index ofrefraction fused therewith, and a minor portion of glass having anotherindex of refraction, and with a. surrounding wall between said last twoportions and the major portion which is substantially perpendicular tothe surface of the lens, said minor portion of glass being embedded andfused in said intermediate portion and with its upper boundary linesubstantially coincident with the upper boundary line of theintermediate portion, substantially as shown.

JAMES H. HAMMON.

